var e,n,p:integer;
procedure puteri;
var  fact:shortint;
begin
fact:=1;
e:=0;
while n div fact <>0 do
begin
fact:=fact*5;
if n div fact=0 then
break;
e:=e+n div fact;
end;
end;
begin
assign (input,'fact.in');
reset (input);
readln (input,p);
close (input);
n:=p*5;
e:=0;
assign (output,'fact.out');
rewrite (output);
while e<>p do
begin
puteri;
if e<>p then
dec (n,5)
else
begin
write (output,n);
break;
end;
end;
close (output);
end.